Supervised electric system



April 1937 H. c. GRANT, JR

SUPERVISED ELECTRIC SYSTEM Original Filed Sept. 22, 1934 iNVENTOR HAP-FYCAMPBELL Gem/r Je.

' ATTORNEY Patented Apr. 20, 1937 SUPERVISED ELECTRIC SYSTEM HarryCampbell Grant, Jr., New York, N. 2., as-

signor to vWalter Kidde & Company, Inc., Bloomfield, N. 5., acorporation of New York Original application September 22, 1934, SerialNo. 145,092. Divided and this application No-' vember 16, 1935; SerialNo. 50,071

swims. (Cl. 117-352) The present invention is a division of applicant'scopending application Serial No. 145,092, filed September 22, 1934, forSupervised electric system, and embodies that portion of the systemillustrated and described in the above cpending application whichrelates to the method of ground protection therein described.

It is accordingly an object-of the presentinvention to provide a methodof ground protection, 10 which is particularly adapted for use withsystems of the type described in my above mentioned 00- pendingapplication.

I It is also an objectof thisinvention. to provide a system which can beelectrically energized 10 either by a main source of electricalpotential, or by a secondary source of electrical potential nor mally'under charge from the main source, the system likewise being capable ofenergization simultaneously by both of the sources of potential. 20 Inthe system shown the reference numerals I and 2 represent the positiveand negative terminals of a secondary source of electrical potential inthe form of a battery 3, which is protected by fuses 4 and 5 and whichis normally under charge,

25 in a manner hereinafter to be described, from amain source ofelectrical energy, the positive and negative terminals of which areshown at 5 and 1.

At A there is indicated a so-called external" 30 circuit comprising apair of parallel wires bridged by normally open circuit closingthermostats 8, which wires will hereinafter be known as outer" and innerwires'in view of their relative positions on the drawing. B and Cindicate addi- 35 tional external circuits, all of which are connectedin series in the following manner; current flowing from the positiveline through the wire 9, the outer ground detecting relay Ill, the wireH, the outer wires of the external circuits A, B 40" and C insuccession, the wire I2, the fire alarm relay l3, the wire 14, theswitch l5, the circuit lamp Ili the wire 11, the switch I5 the circuitlamp It", the wire l8, the switch 15, the circuit lamp li the wire IS,the inner wires of the ex- 45 ternal circuits C, B and A in successionthrough the interposed switches 20 and 2i, the wire 22, the inner grounddetecting relay 23, and the wires 24 and 25 to the negative line.

The circuit just described and the battery 3 50 are connected inparallel with the man supply terminals 6 and 1, the latter normallysupplying the energizing current for said circuit and the chargingcurrent for the battery, the positive and negative junction points beingat 8' and 2.

The path of the charging current for the battery is from the main supplyterminal 6 through the armature 26 of the main supply supervising relay21, the contact '28, the charging resistances 29 and 38, the wires 3|and 32, through the battery, the wires 33, 34, 35 and 3B,the charging"'5 resistances 31 and 38, the wires 39 and 39', the

armature 40, the contact 4|, and' the wires 42,

43 and 44 to the main supply terminal 1; whereby the negative terminalof the battery is at a higher potential than the negative terminal ofthe main supply.

At 45 is shown the battery supervisingrelay l which is connected to thepositive terminal of the battery by wires 32 and 46, and to the negativeterminal of the battery by the wires 41, 34 and 33.

When a system in accordance with the present invention has beeninstalled and is to be made ready for use, the reset switch 48 isclosed, whereupon current flows from the positive terminal of thebattery through the wires 32, 3i and 49, the reset switch 48, the wire50, the main supply supervising relay 21, the wires 5| and 39, thecharging resistance 31-38, and the wires 36, 35, 34 and 33 to thenegative terminal of the battery. This results in energization of themain supply supervising relay 21, causing closing of the contacts 28 and4|. Upon intentional reopening of the reset switch 48, which istherefore preferably of the push-button type, the main supplysupervising relay 21 will be found to be connected across the mainsupply terminals 6 and 1- through the armature 25, the contact 28, thewire 52, the contact 53 of the ground detecting relay ill, the armature54, the contact 55 of the ground detecting relay 23, the armature 55,the wire 51, the resistance 58, the wires 50, 5| and 38', the armature40, the contact 4|, and the wires 42, 43 and 44, thus holding the relay21 energized.

By reason of the herein-referred to flow of current through the externalcircuits from the junction point 8' to the junction point 2, the firealarm relay I3 is normally energized, but as soon as a fire occurs in aspace protected by an external circuit, as for example in the spaceindicated by the normally open circuit closing thermostat 8 on theexternal circuit A, such thermostat will operate to bridge the parallelouter and inner wires of the external circuit A, whereby the fire alarmrelay l3 will be short-circuited and de-energized. This results in theclosing of the contacts 58 and 50 by the armatures 6| and 52, whereuponfire alarm signals are rendered in the following manner. The referencenumeral 63 represents the fire alarm gong which is normally located atthe central fire alarm station. This gong is sounded by reason ofcurrent flowing from the positive line through the wires 64, 65 and 66.the contact 60, the armature 62, and the 5 wires 61 and 25 to thenegative line, the switch 61' being a normally closed switch which willbe referred to hereinafter. fire alarm lamp 68, normally located at thecentral fire alarm station, is illuminated by curl rent flowing from thepositive line through the wires 69 and 66, the contact 60, the armature62,

and-the wires 61 and 25 to the negative line.

In certain types of installations, for example on board ships, it isadvisable to, signal the presl ence of fire to the engine room or someother location than the central fire alarm station, which is normally inthe wheelhouse or chart roomof the ship. For thispurpose there isprovided a second fire alarm gong 10, which becomes energized bycurrentflowing from the positive line through the wires 64 and |l,1 the fuse12, the

wires 13 and I4, the'contact 59, the armature 8|, and the wires 61 andto the negative line. As soon as the presence of fire is made known 25by any one or more of the means provided, the

fire-watch attendant immediately proceeds to the central fire alarmstation, at which point he will find on the operating panel switches l5,l5", ti 20 and 2|, all of which he is to immediately proceed to movefrom their normal positions on the right hand contacts (as contact 11 ofswitch l5) to their positions on'the left hand contacts (as contact 18of switch l5); this operation isolating the inner wires of each circuit,the outer wires being all positive in potential, the ground detectingrelays both being of very low resistance.

If no fire has occurred in any of the spaces protected by the externalcircuit A, so that no thermostat has operated on this circuit, noindication will be given by the circuit lamp It, as this lamp will lacka positive operating potential. If, however, fire has occurred in one ofthe spaces protected by the external circuit A, so that one of thenormally open circuit closing thermostats 8' on the external circuit Ahas operated to bridge the parallel outer and inner wires of the external circuit A, the positive potential of the vouterwire will beapplied to the inner wire and then to the circuit lamp i6 through theswitch 2|, which has been moved by the fire-watch attendant from thecontact 15 to the contact 16; the circuit lamp l6 being connected tonegative through switch l5", which has been moved from contact TI tocontact I8, wire 18 and wire 80; whereby the circuit lamp It will beilluminated, thus indicating the operation of a thermostat on theexternal circuit A and the occurrence of a fire in a space protected bythe circuit.

Similar indications are given in connection with the external circuits Band C, as can be readily understood from the drawing, the correspondingswitches and circuit lamps being indicated by similar referencenumerals.

It has already been mentioned that the external circuits are protectedagainst the occurrence of grounds, and the relays Ill and 23 havealready been referred to as ground detector relays, these relays notbeing normally energized by the relatively small supervisory currentwhich flows through the external circuits from the junction point 9' tothe junction point 2, the voltage drop across each of the relays i0 and23 being only a fraction of the total drop from the junction point 9' tothe junction point 2 by At the same time the reason of the far greaterresistance of thefire alarm relay IS in the same series circuit.

Itis customary in ship installations to have the ships electricalcircuits ground clear but this condition rarely exists. At times theship's negative may be grounded and shortly after this the ground may bechanged from negative to positive. The relative position of the groundon a ships generator and various points of the circuit in accordancewith the present invention will cause diiferent indications to be givenat the central control station.

In order to clarify the discussions which follow, let it be assumed, byway of example, that a shiphas a 220 volt supply and that the battery 3of the present invention is a 40 volt battery.

Let-it also be noted that the battery 3 is normally under charge fromthe main source of supply, in a manner already hereinbefore describedinv greater detail, through a charging resistance 29-30 in the positivelead to the battery and through a charging resistance 31-88 of substantially equal ohmic value in the negative lead to the battery, thatthe potential Of the.

negative terminal of the battery is asmuch higher than the potential ofthe negative terminal I of the main power supply as the potential of thepositive terminal of the battery is lower than the potential of thepositive terminal 8 of the main power supply.

It, therefore, any one of the outer wires oi any of the externalcircuits becomes grounded at the same time the positive side of the mainpower supply is normally grounded, a much greater than normal voltage isapplied across the inner ground detector relay 2!, whereupon the relay23 is energized and the contact at 55 is opened. The opening of eitherthe contact 53 or the contact 55 directly interrupts the alreadydescribed energizing circuit of the main supply supervising relay 21,whereupon the latter is deenergized, opening thecontact at ll, andclosing the contact at 84. This action results in the sounding oi thetrouble gong 88 and the illumination of the trouble lamp 86, by reasonof current flowing from the positive terminal of the battery through thewires 81, II, I! and 90, then in parallel through the trouble gong andthe trouble lamp 86, then through the wires 8| and 92, the contact 84,the armature 40, the wires 39' and 39, the charging resistance 31-", andthe wires 36, 35, 34 and 33 to the negative terminal oi' the battery.The sounding of the trouble gong 85 can be stopped by opening thenormally closed switch 83. but the trouble lamp will remain illuminateduntil the trouble has been repaired.

Similarly, if any one of the outer wires of any of the external cricuitsbecomes grounded while at the same time the negative side of the mainpower supply is normally grounded, a high current will flow through theouter ground detecting relay in, by reason of cutting out of the circuitof the high resistance fire alarm relay II, and the relay ill will beenergized and the contact at 53 opened. If, on the other hand, any oneof the inner wires of any of the external circuits becomes groundedwhileat the same time the negative side of the main power supply isnormally grounded, a high current will flow through the inner grounddetecting relay 23, and the relay 23 will be energized and the contactat 55--opened. The reason that the relay 23 operates is that the lowpotential end of the relay 23 is at the same potential as the negativeterminal of the battery, which latter potential is higher than thepotential of the negative side of the main power supply, as alreadydescribed. The opening of either the contact 53 or the contact 55 hasthe same effect as described in connection with positive grounds.

Although it is one of the purposes of the main supply supervising relay21 to indicate the failure of the main supply, whereby the relay wouldbe de-energized and the trouble signals given in the manner alreadyexplained, the most important function of the relay 21 is to break thecircuit between the fire alarm system and the main supply on both sides,thus removing the ground and allowing the battery to re-energize thefire alarm relay I 3, so that dangerous currents often flowing forground conditions will be interrupted. For this reason the relay 21 isnot arranged to pick up on the main supply voltage directly, but, ifdeenergized, is required to be reset manually by the reset switch 48, asotherwise, upon de-energization of the relay 21 due to a ground withconsequent breaking of the ground circuit, the relay 21 would bere-energized and thus bring back the ground, with the result that therelay would buzz rapidly and burn off either of the contacts 28 or 4|,depending on the relative location of the grounded points.

The relay 21 has also a third function, which is best mentioned at thistime, in that the breaking of the circuit between the fire alarm systemand the main supply upon failure of the main supply prevents the batteryfrom discharging back into the main supply lines, the battery nowserving as the main and only source of energy.

It is to be understood that the detection of grounds in accordance withthe present invention depends upon normal grounding of the positive ornegative of the main source of electrical supply, either directly orthrough a ground resistance of a ground detector arrangement such as issometimes employed, and which consists of two lamps connected in serieswith each other and across the main supply, the connection between thelamps being normally grounded, so that each of the lamps is a referredto ground resistance, and whereby grounding of either line at any pointgives a ground signal by causing the extinguishing of the correspondinglamp and the brightening of the lamp corresponding to the other line.

In view of the fact that the auxiliary fire alarm gong is normallylocated at some distance from the central fire alarm station, defectscan easily occur in the external leads to the auxiliary fire alarm gong,and this gong is accordingly supervised by means of the auxiliary gongsupervising relay 94. current flowing from the positive line through thewire 64, the external gong lead 1|, the auxiliary fire alarm gong 10,the fuse 12, the wire 13, the auxiliary gong supervising relay 94, andthe wires 95, 61 and 25 to the negative line. 1

It now the main supply is normally grounded on the negative side, and ifa ground occurs in the external gong lead 11', the auxiliary gongsupervising relay 94 will be short-circuited and consequentlytie-energized, whereby the armature 96 will close the contact 81, andthe trouble,

gong and trouble lamp will be operated by reason of current flowing fromthe positive line through the trouble gong and trouble lamp in parallel,the

wires 9| and 98, the contact 91, the armature 96, and the wires 95, 61and 25 to the negative line. At the same time the auxiliary gong 10 willsound due to the cutting out of the high resistance of the supervisingrelay 94. If, however, a ground occurs in the external gong lead H, suchground will constitute a direct short-circuit across the battery 3 andone of the fuses 4 and 5 will blow out, whereupon the batterysupervising relay 45 will be energized and will give the trouble signalin a manner hereinafter to be described.

If,instead of the main supply line being normally grounded on thenegative side, it is normally grounded on the positive side, a ground inthe external gong 1| will cause the auxiliary gong to sound by reason ofthe increased voltage to which it will be subjected. On the other hand,if the external gong lead 1| becomes grounded, the increased voltage onthe entire system will cause the battery supervising relay 45 to beenergized and the trouble signal given in a manner hereinafter tobedescribed. At the same time the abnormally high charging current willcause one of the fuses 4 and 5 to blow, thus protecting the batteryagainst excessive charge.

The external gong leads are not only protected against grounds in themanner already described,

but likewise against direct short-circuits of the leads. Such ashort-circuit 'is normally undetected, but as soon as a fire alarmsignal is given,

' the short-circuit of the auxiliary gong leads cona considerableincrease in voltage across the relay winding.

It has already been explained that the externalcircuit between thejunction points 9 and I, and the battery 3, are connected in parallelacross the main supply terminals, 6 and 1, so that normally the mainsupply terminals provide the supervisory current flowing through theexternal circuit and the charging current flowing into the battery..When, however, a fire alarm or trouble alarm is given, the increasedcurrent required by the alarm gongs isgreater than can be supplied bythe main supply. The charging current normally flowing intothe batterytherefore reverses itself and the battery =supplies the excess currentrequired when alarm conditions arise. I

If now thebattery should fail for any reason, not only will the batterysupervising relay 45 be energized and give the trouble signals, but aportion of each of the charging resistances 29-3'0'and 31-38 will be cutout of the main supply line, so that the main supply, will be capableof'supplying the increased current required when alarm conditions arise.

The battery supervising relay 4! is energized uponfailure of thebattery, both when the system is in its otherwise normal condition andwhen fire alarm or trouble alarm ,conditions exist. The manner in whichthe battery supersov In the'system herein described, the resistance byopening the switch visln'g relay is thus energized will be betterunderstood ,if it is kept in mind that the voltage across the relaywinding is normally the same as the voltage across the battery andacross the external circuit between the junctions 9 and 2.

of the external circuit is considerably greater than the internalresistance of the battery, and is also somewhat greater than thecombined values of the charging resistances 29-30 and 31-38. It alsohappens that in the system described the internal resistance of thebattery is less than the combined values of the charging resistances29-30 and 3138. When, there'- fore, the battery fails for any reasonwith the.

substitution of practically infinite resistance in place of the normallysmall internal resistance of the battery, a considerably increasedvoltage drop will occur across the external circuit, due to the factthat removal of the battery charging current load will reduce thevoltage drop across the charging resistance 29-30, and this increasedvoltage, occurring likewise across the winding of the relay 45, willcause the relay to pick up its armatures 99, I and IOI and close thecontacts at I02, I03 and I04. The trouble signals will then be given byreason of current flowing from the positive line through the troublegong and trouble lamp in parallel, the wire 9| one side of the switch93, the resistance I05, the wire I03, the contact I04, the armature IN,and the wires I01, 43 and 44 to the main supply terminal 1. Instead,however, of the connections from the main supply terminals 6 and 1 beingthrough the charging resistances 29-30 and 31-33, the increased currentwhich the main supply is called upon to supply when the fire ortrouble-gongs are sounded, requires that part ofv the chargingresistances be by-passed, and it will accordingly be found that theportion 30 of, the charging resistance 2930 is shirt-circuited byclosing of. the contact I02, the path of the short-circuit being fromone side of the resistance 30 through the wire I08, the contact I02, thearmature 99-, and the wires I09, 46 and 3| to the other side of theresistance 30.

Similarly, the portion 31 of the charging re-' sistance 31*38 isshort-circuited by closing of the contact I03, the path of theshort-circuit being from one side of the resistance 31 through the wireH0, the contact 103, the armature I00, and the wire III to the otherside ofthe resistance 31. If now the trouble gong be stopped 93,additional resistance must be drawn into the circuit to protect thetrouble lamp 83, and this additional resistance will be found at I I2,so that the trouble lamp is energized in a series circuit including theresistances I05 and H2.

It must of course be understood that the main supply now furnishescurrent at an increased voltage across the entire fire alarm system.Con- .must be so designed with respect to the fire sequently, the grounddetector relays I0 and 23 alarm relay I3 that, except when grounds occurin the external circuits, the voltage drop across the relays I0 and 23is only a fraction of the voltage drop between the Junction points 9'and 2. If thisieature is not provided for, failure of the battery withresultant increased voltage on the fire alarm system, as alreadydescribed, would cause energi'zation ofthe ground detector relays I0an'd-23 and de-energization oi the main supply supervising relay 21,- withconsequent cutting oif of themain supply. This would mean that thesystem would be absolutely dead and tric potential, at least one pole ofwhich may be normally grounded, for normally energizing said externalcircuits, a secondary source of electric potential for energizing saidexternal circuits, in the event .of failure of the first named source,normally under charge from the first named source, an electromagnet, analarm signal, means to control the alarm signal by the electromagnet, apair of ground detecting relays; means to connect certain of theaforesaid elements in a series circuit comprising in the following orderone of the ground detecting relays, at least one external circuit, saidelectromagnet, at least one other external circuit, the other grounddetecting relay and the first named source of electric potential; a mainsupply relay, two normally closed pairs of contacts controlled by saidmain supply relay, a normally closed pair of contacts controlled by eachground detecting relay, said main supply relay being normally energizedby reason of connection from one of the poles of the first named sourceof electric potential, through one of the pairs of contacts of the mainsupply relay, in series through the pairs of contacts controlled by theground detecting relays, through the'main supply relay, through thesecond pair of contacts of the main supply relay to the other pole ofthe first named source of electric potential, said of electric potentialis grounded will actuate either one or the other of the ground detecting.relays to open the normally closed'pair of contacts controlled thereby,causing deenergization of the main supply relay and consequentdisconnection of the electric system from both poles of the first namedsource of electric potential together with disconnection from thenormally existing ground, at the same'time permitting the entireelectric system to function from the secondary source of electricpotential despite the disconnection of the first named source ofelectric potential and the existence of the accidental ground.

2. A supervised electric system comprising a plurality of externalcircuits, 8. source of electric potential, at least one pole of 'whichmay be normally grounded, for normally energizing said externalcircuits, a secondary source of electric potential for energizing saidexternal circuits, in the event of failure of the fir'stnamed source,normally under charge from-thefirst named source through chargingresistances in the posisource, so that the relative potential of thenegative terminal of the secondary source is higher than the potentialof the negative terminal of the first named source, an electromagnet, analarm signal, means to control the alarm signal by the electromagnet, apair of ground detecting relays; means to connect certain of theaforesaid elements in a series circuit comprising in the following ordera charging resistance, one of the ground detecting relays, at least oneexternal circuit, said electromagnet, at least one other externalcircuit, the other ground detecting relay, another charging resistance,and the first named source of electric potential; and means controlledby the ground-detecting relays upon the occurrence of a ground in anyone of the external circuits while one of the poles of the first namedsource is grounded to effect disconnection of the electric system fromboth poles of the first named source of electric potential together withdisconnection from the normally existing ground, at the same timepermitting the entire system to function from the secondary source orelectric potential despite the disconnection of the first named sourceof electric potential and the existence of the accidental ground.

3. A supervised electric system comprising a plurality of externalcircuits, a. source of electric potential, at least one pole of whichmay be normally grounded, for normally energizing said externalcircuits, an electromagnet, an alarm signal, means to control the alarmsignal by the electromagnet; a pair of ground detecting relays; means toconnect certain of the aforesaid elements in a series circuit comprisingin the following order one of the ground detecting relays, at least oneexternal circuit, said electromagnet, at least one other externalcircuit, the other ground detecting relay, and the source of 40 electricpotential; a main supply relay, two normally closed pairs of contactscontrolled by said main supply relay, a normally closed pair of contactscontrolled by each ground detecting relay, said main supply relay beingnormally energized by reason of connection from one .0! the poles of thesource of electric potential, through one of the pairs of contacts ofthe main supply relay, in series through the pairs of contactscontrolled by the ground detecting relays, through the main supplyrelay, through the second pair of contacts of the main supply relay tothe other pole of the source of electric potential, said series circuitthrough the ground detecting relays including said pairs of contacts ofthe main supply relay, whereby the occurrence of a ground, in any one ofthe external circuits while one of the poles of the source of electricpotential is grounded will actuate either .one or the other of theground detecting relays to open the normally closed pair of contactscontrolled thereby, causing deenergization of the main supply relay andconsequent disconnection of the electric system from both poles .of thesource of electric potential together with disconnection irom thenormally existing ground.

4. In an electric system comprising a plurality of external circuits, asource-of electric potential, at least one pole of which may be normallygrounded, for normally energizing said external circuits, anelectromagnet, an alarm signal, means to control the alarm signal by theelectromagnet, and means to connect certain of the aforesaid elements ina series circuit comprising at least one external circuit, saidelectromagnet, at least one other external circuit, and the source ofelectric potential; the provision of means for protecting the electricsystem against the occurrence of grounds in an external circuit,comprising a relatively high resistance inserted at each end of theseries circuit adjacent its pointof electrical connection with thesource of electric potential, each said resistance consisting, in partat least, in a ground detecting relay, said resistances serving to limitcurrents flowing when a ground occurs in an external circuit, and meanscontrolled by the operation of said ground detecting relays todisconnect the electric system from the source upon the occurrence of aground in an external circuit at the same time that one of the poles ofthe source is grounded.

HARRY CAMPBELL GRANT, Jn.

